Abstract: A vapor chamber heat spreader includes an evaporator plate, a condenser plate, and a plurality of sidewalls extending from the evaporator plate to the condenser plate to define a vapor chamber. An evaporator wick is coupled to an evaporating surface of the evaporator plate and a thermal compensation layer is coupled to an inner surface of the sidewalls. The thermal compensation layer comprising a plurality of core-shell phase change particles embedded in a metal. The core-shell PC particles include a core that includes a PCM having a phase change temperature of from 50° C. to 250° C. and a shell encapsulating the core. A heat transfer fluid is disposed within the vapor chamber. The vapor chamber heat spreader exhibits superior transient thermal response compared to commercially available heat spreaders. A power electronics assembly includes an electronics device coupled to a surface of the vapor chamber heat spreader.